Fix/improve .gemspec, add needed require 'dnsruby/version'.

* Add require 'dnsruby/version' in dnsruby.rb, was a problem when used as installed gem.
* Change author name format to "First Last" as per convention.
* Correct author email address.
* Remove rubyforge project name, no longer needed.
* Add gem multiline description.
* Remove check for 'CVS', 'svn', no longer needed.
* Make test for 'rdoc' more precise (require it be end of line).
* Remove autorequire script name, obsolete.
* Fix rake dependency version specification.